vacuum dryer to produce high-quality dried fruits and vegetables

Food drying uses much energy and is considered a high carbon footprint process. Solar drying is sustainable, but the dryers must be improved to produce high-quality foods in short times. In this study, a hybrid-solar vacuum dryer was designed, built, and applied to fruit dehydration. dried fruits and vegetables

The dryer was also tested for persimmons and carrots. The drying of all the fruit and vegetable samples resulted in dried and crisp products in 3–4 h, depending on the drying temperature, and the use of continuous electric support for temperatures higher than 70 °C. The hybrid solar dryer operating under vacuum is an innovative and clean technology that results in high-quality products and has excellent potential to be used in small farms.

Dehydration is widely used to preserve fruits and vegetables since the reduction of both their moisture content and water activity increases their shelf-lives significantly. For that, fresh foods are dried to reach a water activity that prevents microorganisms’ growth and considerably reduces chemical and enzymatic reactions. Besides, drying adds value to fruits and vegetables and reduces storage and transportation costs, which is very important in countries with deficient transport systems. Therefore, food drying can be an opportunity to add value to products from small producers. If fruits and vegetables are dried where they are produced, this may reduce food losses and help small farmers to have a higher income.

Food drying can be performed by different processes, such as convective drying, vacuum drying, and freeze-drying. Nevertheless,during processing, undesirable changes in the sensory and nutritional properties of the food commonly occur. Convective drying is relatively cheap and is extensively used for the dehydration of fruits and vegetables. However, the long drying times and the relatively high temperatures of the air-drying cause product shrinkage and may damage theproduct’s sensory and nutritional properties.

Therefore, this study aimed to develop a hybrid-solar-vacuum dryer,with solar collectors (for water heating) and electric energy supplied by any source to dehydrate foods using conductive multiflash drying (KMFD) for obtaining dried-and-crispy fruits and vegetables with high quality in short times. Therefore, banana samples were dried by different process conditions and equipment configuration. Later, the dried samples were analyzed for microstructure and texture. The process and configuration of the equipment that resulted in the best properties of dried bananas were chosen to investigate whether other foods could be dried in this innovative drying system.

The hybrid-solar-vacuum dryer designed and validated for the drying of fruits and vegetables works very well. Slices of banana,persimmon, and carrot can be uniformly dried in approximately 4 h,resulting in crisp and attractive products.